This invention relates generally to a drive system for a hybrid electric motor vehicle. More particularly, it relates to a drive system having two power sources, preferably an internal combustion engine and an electric machine.
To reduce the volume of pollutants exhausted into the air by automotive powertrains driven exclusively by an internal combustion engine, hybrid powertrains that include an electric motor and an IC engine, which operate independently or and in combination, have been developed.
Most electric hybrid vehicles currently available commercially are front wheel drive (FWD) vehicles, in which only the front wheels are driven. A need exists for hybrid electric powertrains applicable to rear wheel drive (RWD) vehicles, four-wheel drive (4WD), and all-wheel drive (AWD) vehicles. Current designs for hybrid electric RWD and AWD applications involve the use of multiple electric machines, each of which operates alternately as a motor and a generator. Often these designs require extensive modification of a transmission, which transmits power to the rear wheels or to a transfer case located rearward of the transmission.
A need exists for a low-cost, hybrid electric powertrain that can be fitted to an existing automatic RWD transmission. To minimize cost, a single electric machine would provide all hybrid functions including electric energy generation, electric vehicle launch, engine starting, electric boosting of engine power, and regenerative braking.